Mobile communication system

ABSTRACT

Appropriate performance is required for “Inter-Frequency Measurement” in accordance with the conditions of a cell to be subjected to “Inter-Frequency Measurement”. A mobile communication system according to the present invention is configured to separately specify the performance required for “Inter-Frequency Measurement” to be used in “Inter-frequency Handover” control between macrocells #11 and #12 and the performance required for “Inter-frequency Handover” to the cell #11B which is not set as an Scell within the coverage area of the macrocell #11.

TECHNICAL FIELD

The present invention relates to a mobile communication system.

BACKGROUND ART

In LTE (Long Term Evolution), it has been considered to dispose cells(e.g., cells #11A and #11B), which are each operated by a capacity bandfor improving the throughput in a hot spot, in a coverage area of a cell(e.g., a cell #11) operated by a coverage band supporting a wide area,as shown in FIG. 1.

In such an environment, as shown in FIG. 2, a mobile station UE in“RRC_Connected state” in the cell #11 operated in a frequency f1 isexpected to perform “Inter-Frequency Measurement” in the cells #11A and#11B disposed in the coverage area of the cell #11, in order todetermine whether or not the cells #11A and #11B can be added as Scellsin CA (Carrier Aggregation).

PRIOR ART DOCUMENT Non-Patent Document

Non-patent document 1: 3GPP contributed article R2-115745

Non-patent document 2: 3GPP Specification TS36.133

SUMMARY OF THE INVENTION

Since the coverage areas of the cells #11A and #11B are generally muchsmaller than that of the cell #11, there may be a case, depending on thelocation of the mobile station UE in the cell #11, where the mobilestation UE does not set the cells #11A and #11B as Scells, or sets thecells #11A and #11B as Scells but does not activate them.

However, current LTE is provided without the assuming such cases, andonly one kind of performance required for “Inter-Frequency Measurement”is specified.

Thus, in current LTE, the same performance is required for“Inter-Frequency Measurement” to be used for control of inter-frequencyhandover between macrocells in coverage bands and for “Inter-FrequencyMeasurement” for a cell not set as an Scell.

Here, the performance required for such “Measurement” includemeasurement accuracy, a measurement cycle, a cycle of measurement resultreport to an upper layer, the number of cells to be measured, themaximum number of measurement frequencies (only in the case ofinter-frequency measurement), and the like.

In other words, the mobile station UE needs to perform “Inter-FrequencyMeasurement” for the cell not set as the Scell at an equal level to“Inter-Frequency Measurement” to be used for inter-frequency handovercontrol between the macrocells in the coverage bands, which leads to aproblem that the mobile station UE has to consume large power.

The present invention has been made in view of the above-mentionedproblem. An objective of the present invention is to provide a mobilecommunication system capable of requiring appropriate performance of“Inter-Frequency Measurement” according to the conditions of a cell tobe subjected to “Inter-Frequency Measurement”.

A first feature of the present invention is summarized as a mobilecommunication system configured to be able to perform carrieraggregation using a primary cell and a secondary cell operated bydifferent frequency carriers, in which the mobile communication systemseparately specifies performance required for inter-frequencymeasurement used for inter-frequency handover control between macrocellsand performance required for measurement of a cell not set as thesecondary cell within a coverage area of each of the macrocells.

A second feature of the present invention is summarized as a mobilecommunication system configured to be able to perform carrieraggregation using a primary cell and a secondary cell operated bydifferent frequency carriers, in which the mobile communication systemseparately specifies first performance required for measurement of anactivated secondary cell, second performance required for measurement ofa secondary cell which is set but not activated, and third performancerequired for measurement of a cell which is not set as the secondarycell, and each of the first performance, the second performance and thethird performance includes measurement accuracy and a measurement cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall configuration diagram of a mobile communicationsystem according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an example of performance requiredfor “Measurement” in the mobile communication system according to thefirst embodiment of the present invention.

FIG. 3 is a diagram for explaining an example of performance requiredfor “Measurement” in a mobile communication system according to ModifiedExample 1 of the present invention.

FIG. 4 is a diagram for explaining a measurement process performed by amobile station in a conventional mobile communication system.

MODE FOR CARRYING OUT THE INVENTION

(Mobile Communication System according to First Embodiment of theInvention)

With reference to FIGS. 1 and 3, a mobile communication system accordingto a first embodiment of the present invention is described.

As shown in FIG. 1, the mobile communication system according to thisembodiment supports LTE-Advanced, and is configured to be able toperform “CA” using a Pcell and an Scell operated by different frequencycarriers.

Note that the mobile communication system according to this embodimentmay be configured to be able to perform “Inter-band CA” using a Pcelland an Scell operated by carriers in different frequency bands, or maybe configured to be able to perform “Inter-band CA” using a Pcell and anScell operated by carriers in the same frequency band.

Note that the mobile communication system according to this embodimentmay be configured to be able to perform “Inter-band CA” using a Pcelland Scells operated by carriers in the same frequency band.

As shown in FIG. 1, in the mobile communication system according to thisembodiment, radio base stations eNB#1 to eNB#3 manages cells #11 to #33and cells #11A to #33B.

Here, the cells #11 to #33 are cells (e.g., macrocells) operated by acoverage band supporting a wide area, for example, by a carrier of afrequency f1 (PCC: Primary Component Carrier).

On the other hand, the cells #11A to #33B are cells (e.g., picocells)disposed within coverage areas of the cells #11 to #33 and operated bycapacity bands for improving the throughput in hot spots, for example,by carriers of frequencies f2 and f3 (SCC: Secondary Component Carrier).

In the example of FIG. 2, the cell #11 operated by the carrier havingthe frequency f1 is set as the Pcell for the mobile station UE, whilethe cell #11A operated by the carrier having the frequency f2 is set asthe Scell for the mobile station UE and activated.

Note that the cell #11B is operated by the carrier having the frequencyf3 and the radio base station eNB determines, based on the location ofthe mobile station UE within the cell #11, whether or not toadditionally set and activate the cell #11B as the Scell for the mobilestation UE.

Also, in the example of FIG. 2, the mobile station UE is moved fromPoint A, to Point B, to Point C, and to Point D within the cell #11.

Furthermore, in the example of FIG. 2, the radio base station eNB doesnot additionally set the cell #11B as the Scell for the mobile stationUE until the mobile station UE reaches Point B within the cell #11.

Thereafter, the radio base station eNB additionally sets the cell #11Bas the Scell for the mobile station UE when the mobile station UEreaches Point B within the cell #11.

Then, the radio base station eNB activates the cell #11B as the Scellfor the mobile station UE when the mobile station UE reaches Point Cwithin the cell #11.

Also, the mobile station UE performs “Measurement” in the cells #11 and#12 as well as “Measurement” in the cells #11A and #11B disposed in thecoverage area of the cell #11.

More specifically, the mobile station UE performs “Inter-FrequencyMeasurement” for the cell #11B which is not set as the Scell in the areafrom Point A to Point B within the cell #11 (Case 1).

Moreover, the mobile station UE performs “Intra-Frequency Measurement”for the cell #11B which is set as the Scell but not activated in thearea from Point B to Point C within the cell #11 (Case 2).

Furthermore, the mobile station UE performs “Intra-FrequencyMeasurement” for the cell #11B activated as the Scell in the area fromPoint C to Point D within the cell #11 (Case 3).

Here, LTE (Release-10) is specified such that equal performance(Performance Specification B) is required for “Inter-FrequencyMeasurement” to be used for “Inter-Frequency Handover” control betweenthe macrocells #11 and #12 in the coverage bands and for“Inter-Frequency Measurement (Case 1)” for a cell which is not set as aScell.

Note that, in the present specification, the performance required forsuch “Measurement” includes measurement accuracy, a measurement cycle, acycle of measurement result report to an upper layer, the number ofcells to be measured, the maximum number of measurement frequencies(only in the case of inter-frequency measurement), and the like.

In contrast to this, the mobile communication system according to thisembodiment is configured to separately specify the performance(Performance Specification A) required for “Inter-Frequency Measurement”to be used for “Inter-Frequency Handover” control between the macrocells#11 and #12 in the coverage bands and the performance (PerformanceSpecification B) required for “Inter-Frequency Measurement (Case 1)” fora cell which is not set as a Scell.

For example, in the mobile communication system according to thisembodiment, as shown in FIG. 2, Performance Specification A may specifythe measurement cycle as “3200 ms” and the measurement accuracy of RSRP(Reference Signal Received Power)/RSRQ (Reference Signal ReceivedQuality) as “±3 dB (Es/lot≧0 db)”.

Also, in the mobile communication system according to this embodiment,as shown in FIG. 2, Performance Specification B may specify themeasurement cycle as “1600 ms” and the measurement accuracy of RSRP/RSRQas “±3 dB (Es/lot≧6 dB)”.

In other words, as shown in FIG. 2, the mobile communication systemaccording to this embodiment may be configured such that the measurementcycle specified by Performance Specification B is shorter than themeasurement cycle specified by Performance Specification A.

Also, as shown in FIG. 2, the mobile communication system according tothis embodiment may be configured such that the measurement accuracyspecified by Performance Specification B is higher than the measurementaccuracy specified by Performance Specification A.

Note that, in current LTE, “measCycleScell-r10” set in “MeasObjectEUTRA”in “Measurement Configuration” can be used to set a measurement cycle of“Deactivated Scell Measurement (Case 2)” in a cell which is set as anScell but not activated.

Here, “Deactivated Scell Measurement” means “Intra-FrequencyMeasurement” in the Scell which is set but not activated.

In contrast to this, the mobile communication system according to thisembodiment may be extended such that “measCycleScell-r10” describedabove can be used to set not only the measurement cycle of “DeactivatedScell Measurement (Case 2)” in a cell set as an Scell but not activatedbut also a measurement cycle of “Inter-Frequency Measurement (Case 1)”in a cell not set as an Scell.

The invention according to this embodiment can require appropriateperformance of “Inter-Frequency Measurement” according to the conditionsof a cell to be measured.

MODIFIED EXAMPLE 1

With reference to FIG. 3, a mobile communication system according toModified Example 1 of the present invention is described. The mobilecommunication system according to Modified Example 1 is described belowby focusing on differences from the mobile communication systemaccording to the first embodiment described above.

As shown in FIG. 3, a mobile station UE performs “Measurement” in a cell#11 as well as “Measurement” in cells #11A and #11B disposed in acoverage area of the cell #11.

More specifically, the mobile station UE performs “Inter-FrequencyMeasurement” for the cell #11B which is not set as the Scell in the areafrom Point A to Point B within the cell #11 (Case 1).

Moreover, the mobile station UE performs “Deactivated Scell Measurement”for the cell #11B which is set as the Scell but not activated in thearea from Point B to Point C within the cell #11 (Case 2).

Furthermore, the mobile station UE performs “Intra-FrequencyMeasurement” for the cell #11B activated as the Scell in the area fromPoint C to Point D within the cell #11 (Case 3).

For the above cases, the mobile communication system according to thisembodiment is configured to separately specify the performance requiredfor “Intra-Frequency Measurement (Case 3)” for the activated Scell(Performance Specification C), the performance required for “DeactivatedScell Measurement (Case 2)” for the Scell which is set but not activated(Performance Specification B), and the performance required for“Inter-Frequency Measurement (Case 1)” for the cell which is not set asthe Scell (Performance Specification A).

For example, in the mobile communication system according to thisembodiment, as shown in FIG. 3, Performance Specification A may specifythe measurement cycle as “3200 ms” and the measurement accuracy of RSRP(Reference Signal Received Power)/RSRQ (Reference Signal ReceivedQuality) as “±3 dB (Es/lot≧0 dB)”.

Also, in the mobile communication system according to this embodiment,as shown in FIG. 3, Performance Specification B may specify themeasurement cycle as “1600 ms” and the measurement accuracy of RSRP/RSRQas “±3 dB (Es/lot≧6 dB)”.

Moreover, in the mobile communication system according to thisembodiment, as shown in FIG. 3, Performance Specification C may specifythe measurement cycle as “200 ms” and the measurement accuracy ofRSRP/RSRQ as “±3 dB (Es/lot≧6 dB)”.

As shown in FIG. 3, the mobile communication system according to thisembodiment may be configured such that the measurement accuracy ofRSRP/RSRQ specified by Performance Specification B becomes equal to themeasurement accuracy of RSRP/RSRQ specified by Performance SpecificationC.

Moreover, as shown in FIG. 3, the mobile communication system accordingto this embodiment may be configured such that the measurement cyclespecified by Performance Specification C is shorter than the measurementcycle specified by Performance Specification B.

Furthermore, as shown in FIG. 3, the mobile communication systemaccording to this embodiment may be configured such that the measurementcycle specified by Performance Specification B is shorter than themeasurement cycle specified by Performance Specification A.

Note that, in current LTE, “measCycleScell-r10” set within“MeasObjectEUTRA” in “Measurement Configuration” can be used to set ameasurement cycle of “Deactivated Scell Measurement (Case 2)” in thecell which is set as the Scell but not activated.

In contrast, the mobile communication system according to thisembodiment may be extended such that “measCycleScell-r10” describedabove can be used to set not only the measurement cycle of “DeactivatedScell Measurement (Case 2)” in the cell which is set as the Scell butnot activated but also a measurement cycle of “Inter-FrequencyMeasurement (Case 1)” in the cell which is not set as the Scell.

The invention according to this embodiment can separately specifyPerformance Specifications A to C for Cases 1 to 3 shown in FIG. 2, andthus can require appropriate performance of “Measurement” according tothe conditions of a cell to be measured.

The above-described features of the embodiment may also be expressed asfollows.

A first feature of the embodiment is summarized as a mobilecommunication system configured to be able to perform CA (carrieraggregation) using a Pcell (primary cell) and a Scell (secondary cell)operated by different frequency carriers, in which the mobilecommunication system separately specifies performance required for“Inter-Frequency Measurement” used for “Inter-Frequency Hanover” controlbetween macrocells #11 and #12 and performance required for“Inter-Frequency Handover” (measurement) of a cell #11B not set as theScell within a coverage area of each of the macrocells #11.

A second feature of the embodiment is summarized as a mobilecommunication system configured to be able to perform CA using a Pcelland a Scell operated by different frequency carriers, in which themobile communication system separately specifies first performancerequired for “Measurement” of an activated Scell, second performancerequired for “Measurement” of a Scell which is set but not activated,and third performance required for “Measurement” of a cell which is notset as the Scell, and each of the first performance, the secondperformance and the third performance includes measurement accuracy anda measurement cycle.

In the second feature of the embodiment, the mobile communication systemspecifies the performance such that the measurement accuracy included inthe first performance is equal to the measurement accuracy included inthe second performance.

It should be noted that the foregoing operations of the mobile stationUE and the radio base station eNB may be implemented by hardware, maybeimplemented by a software module executed by a processor, or may beimplemented in combination of the two.

The software module may be provided in a storage medium in any format,such as a RAM (Random Access Memory), a flash memory, a ROM (Read OnlyMemory), an EPROM (Erasable Programmable ROM), an EEPROM (ElectronicallyErasable and Programmable ROM), a register, a hard disk, a removabledisk, or CD-ROM.

The storage medium is connected to a processor so that the processor canread and write information from and to the storage medium. Instead, thestorage medium may be integrated in a processor. The storage medium andthe processor may be provided inside an ASIC. Such an ASIC may beprovided in the mobile station UE and the radio base station eNB.Otherwise, the storage medium and the processor may be provided asdiscrete components inside the mobile station UE and the radio basestation eNB.

Hereinabove, the present invention has been described in detail by useof the foregoing embodiments. However, it is apparent to those skilledin the art that the present invention should not be limited to theembodiments described in the specification. The present invention can beimplemented as an altered or modified embodiment without departing fromthe spirit and scope of the present invention, which are determined bythe description of the scope of claims. Therefore, the description ofthe specification is intended for illustrative explanation only and doesnot impose any limited interpretation on the present invention.

Note that the entire content of Japanese Patent Application No.2012-017378 (filed on Jan. 30, 2012) is incorporated by reference in thepresent specification.

INDUSTRIAL APPLICABILITY

As described above, the present invention can provide a mobilecommunication system capable of requiring appropriate performance of“Inter-Frequency Measurement” according to the conditions of a cell tobe subjected to “Inter-Frequency Measurement”.

EXPLANATION OF THE REFERENCE NUMERALS

UE mobile station

eNB radio base station

1. A mobile communication system configured to be able to performcarrier aggregation using a primary cell and a secondary cell operatedby different frequency carriers, wherein the mobile communication systemseparately specifies performance required for inter-frequencymeasurement used for inter-frequency handover control between macrocellsand performance required for measurement of a cell not set as thesecondary cell within a coverage area of each of the macrocells.
 2. Amobile communication system configured to be able to perform carrieraggregation using a primary cell and a secondary cell operated bydifferent frequency carriers, wherein the mobile communication systemseparately specifies first performance required for measurement of anactivated secondary cell, second performance required for measurement ofa secondary cell which is set but not activated, and third performancerequired for measurement of a cell which is not set as the secondarycell, and each of the first performance, the second performance and thethird performance includes measurement accuracy and a measurement cycle.3. The mobile communication system according to claim 2, wherein themobile communication system specifies the performance such that themeasurement accuracy included in the first performance is equal to themeasurement accuracy included in the second performance.